1. Field of the Invention
The present invention pertains to the generation of electrical power. In particular, this invention relates to distributed power generation systems for use close to where electricity is used (e.g., a home or business) to provide an alternative to or an enhancement of the traditional electric power system.
2. Description of Related Art
Centralized electric power generating plants provide the primary source of electric power supply for most commercial, agricultural and residential customers throughout the world. These centralized power-generating plants typically utilize an electrical generator to produce electrical power. The generator has an armature that is driven by conversion of an energy source to kinetic energy, such as a water wheel in a hydroelectric dam, a diesel engine or a gas turbine. In most cases, steam is used to turn the armature, and the steam is created either by burning fossil fuels (e.g., oil, coal, natural gas, etc.) or through nuclear reaction. The generated electrical power is then delivered over a grid to customers that may be located great distances from the power generating plants. Due to the high cost of building and operating electric power generating plants and their associated power grid, most electrical power is produced by large electric utilities that control distribution for defined geographical areas.
In recent years, however, there has been a trend away from the centralized model of electric power generation toward a distributed power generation model. One reason for this trend is the inadequacy of the existing electric power infrastructure to keep pace with soaring demand for high-quality, reliable power. Electric power distributed in the traditional, centralized manner tends to experience undesirable frequency variations, voltage transients, surges, dips or other disruptions due to changing load conditions, faulty or aging equipment, and other environmental factors. This electric power is inadequate for many customers that require a premium source of power (high quality) due to the sensitivity of their equipment (e.g., computing or telecommunications providers) or that require high reliability without disruption (e.g., hospitals). The utilities that traditionally operate centralized power generating plants are increasingly reluctant to make the large investments in modernized facilities and distribution equipment needed to improve the quality and reliability of their electric power due to regulatory, environmental, and political considerations.
More recently, technological advancements in small-scale power generating equipment has led to greater efficiencies, environmental advantages, and lower costs for distributed power generation. Various technologies are available for distributed power generation, including turbine generators, internal combustion engine/generators, microturbines, photovoltaic/solar panels, wind turbines, and fuel cells. Distributed power generating systems can complement centralized power generation by providing incremental capacity to the utility grid or to an end user. By installing a distributed power generating system at or near the end user, the electric utility can also benefit by avoiding or reducing the cost of transmission and distribution system upgrades. For the end user, the potential lower cost, higher service reliability, high power quality, increased energy efficiency, and energy independence are all reasons for interest in distributed power generating systems.
There are numerous applications for distributed power generating systems. A primary application is to produce premium electric power having reduced frequency variations, voltage transients, surges, dips or other disruptions. Another application is to provide standby power (also known as an uninterruptible power supply or UPS) used in the event of a power outage from the electric grid. Distributed power generating systems can also provide peak shaving, i.e., the use of distributed power during times when electric use and demand charges are high. In such cases, distributed power can be used as baseload or primary power when it is less expensive to produce locally than to purchase from the electric utility. By using the waste heat for existing thermal processes, known as co-generation, the end user can further increase the efficiency of distributed power generation.
Notwithstanding these and other advantages of distributed power generation, there are other disadvantages that must be overcome to achieve wider acceptance of the technology. Conventional distributed power generating systems require further improvements in reliability and efficiency in order to compete effectively with centralized power generation. Distributed power generating systems that utilize an engine to drive a generator tend to be slow to achieve an operational speed from start up, and consequently are slow to provide a source of back-up power. During the time necessary to bring the engine and generator up to operational speed, the distributed power generating system must rely on stored power (i.e., batteries) to supply the back-up source. Battery storage systems are large, expensive, heavy, and have relatively short life expectancy. It is therefore desirable to minimize reliance of the distributed power generating system on batteries.
Accordingly, it would be desirable to provide a distributed power generating system to serve as an alternative to or enhancement of centralized power generation that overcomes these and other drawbacks of conventional distributed power generation. More particularly, it would be desirable to provide a distributed power generating system that achieves an operational state very rapidly so as to reduce the reliance on stored power.